As is known in the medical and the pharmaceutical arts, the desiderata of an enteric coat is to protect an orally administered drug from the environment of the stomach. The enteric coat provides protection from the environment of the stomach including its fluids, its acidity, its enzymes and peristaltic agitation in the stomach. It is desirable also for the enteric coat to maintain its integrity during the time needed for the drug to pass through the stomach and enter the intestine.
Heretobefore, enteric coats were used to safeguard a drug in the stomach, but frequently they were not satisfactory. One reason they were not satisfactory is they allowed water transport through the enteric coat causing the drug to be released prematurely. For some dosage forms, such as an osmotic device, the passage of water through the enteric coat hydrates the device and this causes the drug to be released too rapidly and early once the device enters the intestine and the enteric coat disintegrates. Consequently, as a result of this action, the drug may be absorbed or metabolized at the start of the intestine and it is not delivered at a controlled rate throughout the intestine for its intended effect. One effort to overcome this consists in applying thicker enteric coats, however, this too lets fluid flux therethrough and the thicker coats often rupture under the influence of agitation in the stomach.
In view of the above presentation, it is immediately self-evident that a need exists for a dosage form comprising an enteric coat that comprises means for substantially preventing the passage of water through its enteric coat. The need exists for a dosage form comprising an enteric coat that is hydrophobic for preventing the flux of water through the enteric coat particularly during the time the dosage form is in the stomach.